全文获取类型
收费全文 | 381940篇 |
免费 | 2271篇 |
国内免费 | 664篇 |
专业分类
化学 | 180253篇 |
晶体学 | 5669篇 |
力学 | 20949篇 |
综合类 | 10篇 |
数学 | 55329篇 |
物理学 | 122665篇 |
出版年
2020年 | 2805篇 |
2019年 | 3283篇 |
2018年 | 11460篇 |
2017年 | 12127篇 |
2016年 | 9456篇 |
2015年 | 3824篇 |
2014年 | 5612篇 |
2013年 | 12352篇 |
2012年 | 13185篇 |
2011年 | 21747篇 |
2010年 | 14611篇 |
2009年 | 14958篇 |
2008年 | 19576篇 |
2007年 | 22384篇 |
2006年 | 10417篇 |
2005年 | 14136篇 |
2004年 | 11160篇 |
2003年 | 10678篇 |
2002年 | 9144篇 |
2001年 | 9893篇 |
2000年 | 7476篇 |
1999年 | 5543篇 |
1998年 | 4492篇 |
1997年 | 4375篇 |
1996年 | 4235篇 |
1995年 | 3816篇 |
1994年 | 3746篇 |
1993年 | 3596篇 |
1992年 | 4074篇 |
1991年 | 4461篇 |
1990年 | 4222篇 |
1989年 | 4243篇 |
1988年 | 4147篇 |
1987年 | 4161篇 |
1986年 | 3828篇 |
1985年 | 4782篇 |
1984年 | 4832篇 |
1983年 | 4030篇 |
1982年 | 4078篇 |
1981年 | 3850篇 |
1980年 | 3657篇 |
1979年 | 4243篇 |
1978年 | 4436篇 |
1977年 | 4407篇 |
1976年 | 4490篇 |
1975年 | 4166篇 |
1974年 | 4081篇 |
1973年 | 4317篇 |
1972年 | 3189篇 |
1971年 | 2804篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
911.
N. I. Alekseev V. B. Kaplan A. M. Martsinovskii I. I. Stolyarov 《Technical Physics》1997,42(6):599-605
Results are presented from a systematic investigation of the conditions under which anomalously high rates of plasma generation
are observed in the anode region of a low-voltage Knudsen arc in grid plasma switch elements. The phenomenon develops over
a wide range of currents and switched voltages under conditions for which the plasma density in the cathode-grid region is
noticeably higher than the density in the anode region. and its onset is characterized by a pronounced pressure threshold
of ∼2×10−2 Torr. The results are analyzed from the standpoint of the possible mechanisms for anomalous plasma generation — collisional
nonresonance diffusion of electrons in velocity space, leading to enrichment of the distribution function in fast particles,
and the collapse of Langmuir waves in the gap at the high energies of the beam produced when the wires of the grid are bridged
by the quenching pulse and and the current is blocked.
Zh. Tekh. Fiz. 67, 15–21 (June 1997) 相似文献
912.
The dependence of the nonlinear reflection coefficient R of a mirror with a wavefront reversing surface on the intensity I
of the reference wave is analyzed in terms of a phenomenological model of a medium having a nonlinear Fresnel reflection amplitude
coefficient φ. Substantial differences are revealed for media having different signs of the nonlinearity coefficient β=(dφ/dI).
It is shown that R is related to the magnitude D of the dynamic range of the wavefront reversing mirror by the expression
RD=Qs' where Qs is a parameter which defines the “quality” of the nonlinear medium.
Far-Eastern State Academy of Communications. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 68–70,
August, 1997. 相似文献
913.
A. V. Vashkovskii É. G. Lokk V. I. Shcheglov 《Journal of Experimental and Theoretical Physics》1997,84(3):560-568
The propagation of surface and volume magnetostatic waves in unsaturated films of yttrium iron garnet is studied experimentally
for the case when the wavelength greatly exceeds the domain width, while the domain width is comparable to the film thickness.
The characteristics of these waves are examined for symmetric linear, asymmetric linear, and symmetric zigzag strip domain
structures in the films. These characteristics cannot be explained by a theory based on averaging the magnetization over all
the domains.
Zh. éksp. Teor. Fiz. 111, 1016–1031 (March 1997) 相似文献
914.
Structure studies are reported on martensite transformations in porous TiNi alloy made by high-temperatures self-propagating
synthesis. The transformations occur over a large temperature range and are incomplete. The structure data are used in reconstructing
the heat release during the transition, where it is shown that it is determined by the superposition of martensite transformations
occurring locally at various temperatures.
Tomsk State Architectural and Building Academy. Kuznetsov Siberian Technical Physics Institute, Tomsk State University. Translated
from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 20–24, January, 1997. 相似文献
915.
We consider the scalar field φ
t
with a reversible stochastic dynamics which is defined by the standard Dirichlet form relative to the Gibbs measure with
formal energy . The potential V is even and strictly convex. We prove that under a suitable large scale limit the φ
t
-field becomes deterministic such that locally its normal velocity is proportional to its mean curvature, except for some
anisotropy effects. As an essential input we prove that for every tilt there is a unique shift invariant, ergodic Gibbs measure
for the -field.
Received: 1 February 1996 / Accepted: 2 July 1996 相似文献
916.
An all-optical fiber nonlinear Fabry-Perot resonator is proposed. The steady-state model for describing this resonator is developed. The transmission and refection bistabilities are shown numerically. Our results show that the bistability in this system is similar to that in a normal nonlinear Fabry-Perot etalon, except that the characteristics of the bistability can be changed not only by the cavity length but also by the phase shifts of the fiber loop mirrors. 相似文献
917.
The relativistic four-quark equations are found in the framework of the dispersion relation technique. The behaviour of the low-energy four-particle amplitude is determined by its leading singularities in the pair invariant masses. The approximate solutions of these equations using the method based on the extraction of leading singularities of the amplitudes are obtained. The mass values of lowest exotic mesons are calculated. 相似文献
918.
Changes in thin zinc-sulfide films under the action of the γ-radiation of Co60 are studied by investigating electroluminescence spectra of terbium embedded in these films as a luminescent probe. It is
shown that changes in the relation of the intensities of bands, a decrease in their halfwidth and the background component,
and simplification of the spectrum are observed in a short-wave region of the Tb radiation spectrum that corresponds to5D3→7Fj transitions. The same modification of the radiation spectrum is characteristic of ZnS films whose crystalline structure is
ordered in the course of thermal annealing at a temperature of 350°C. Based on the analysis of the data obtained it is inferred
that irradiating the ZnS films with small radiation doses of 104–105 rad leads to the ordering of their crystalline structure due to the elimination of one of the types of structural defects.
Institute of Physics of Semiconductors, National Academy of Sciences of Ukraine, 45, Nauka Ave., Kiev-28, 252650. Translated
from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 338–341, May–June, 1997. 相似文献
919.
The effect of the replacement of MnO2 by Fe2O3 on the oxidation states of iron in some lithium borosilicate glasses were studied using Mössbauer spectroscopy. DTA and infrared measurements showed the presence of two glassy phases, one of them containing iron and the other manganese. The Mössbauer spectra were measured at room temperature for all the glass samples. The spectra revealed the presence of Fe ions only in ferric state in both tetrahedral and octahedral coordination. Also, it was observed that the ratio between the number of iron ions in both coordination states has not changed with the increase of MnO2 content. 相似文献
920.
The diffuse scattering of x rays in a four-layer waveguide-type heterostructure is investigated. The dynamic enhancement of
diffuse scattering is detected experimentally in regions corresponding to the excitation of waveguide modes for both the incident
and scattered waves.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 4, 219–223 (25 August 1997) 相似文献